Radio-operated controller for all electric automatic pilots



S. L. BARlNG-GOULD ETAL RADIO-OPERATED CONTROLLER FOR ALL ELECTRIC AUTOMATIC PILOTS Dec. 2, 1952 2 SHEETS-SHEET 1 Filed March 31, 1947 IF. mutin s o mww y w m M Jww 3n mun E. m. M L,: M mm fi V 5 I/ W m. W. N i A I: M H B 050 k M T zofimoz L. Em mm wu M 016 ZEDP m0 m.r m

IUPDJU s. 1.. BARlNG-GOULD ETAL 20,148 RADIO-OPERATED CONTROLLER FOR ALL ELECTRIC AUTOMATIC PILOTS Dec. 2, 1952 2 SHEETS-SHEET 2 Filed March 31, 1947 wm mObouJwm moh mwzwu .CDUEU mg Patented Dec. 2, 1952 UNITED STATES OFFICE RADIO-OPERATED CONTROLLER FOR ALL ELECTRIC AUTOMATIC PILOTS Application March 31, 1947, Serial No. 738,438

11 Claims.

The present invention relates to an electric automatic pilot adapted to control the operations of an aircraft by means of signals remotely transmitted by radio.

The automatic steering of aircraft by means of automatic pilots is now a common practice. An all electric automatic pilot as described in copending applications Serial Number 516,488, filed December 31, 1943, and Serial Number 516,489, filed December 31, 1943, discloses manually operated means whereby displacement signals for each axis of control are imparted into the automatic pilot to deflect the various craft control surfaces into proper position for initiating the desired turn or change of attitude. It is desirable to be able to impart into the automatic pilot the displacement signals for each axis of control by means of signals remotely transmitted by radio from another plane or from any ground station.

An object of the present invention is to provide novel means whereby remotely transmitted displacement signals for each axis of control are imparted into an all electric automatic pilot to deflect the craft control surfaces into proper position for initiating the desired turn or change of attitude.

Another object of the present invention is to provide means whereby a remotely transmitted displacement signal for a turn is imparted into an all electric automatic pilot to deflect the craft control surfaces into proper position for initiating the desired co-ordinated turn.

Still another object of the present invention is to provide means whereby a remotely transmitted displacement signal for a skid turn is imparted into an all electric automatic pilot to deflect the rudder surface into proper position for initiating the desired skid turn.

A further object of the present invention is to provide means whereby a remotely transmitted displacement signal for a climb or dive is imparted into an electric automatic pilot to deflect the elevator surfaces into proper position for initiating a climb or dive.

A still further object of the present invention is to provide novel means whereby in response to a remotely transmitted displacement signal for either a co-ordinated or skid turn imparted into an electric automatic pilot, primary control of the turn by the direction control instrument is removed until a remotely transmitted signal for termination of operation is introduced to the direction control instrument to maintain the craft automatically on its new course.

Another objective of'the present invention is to provide means whereby a remotely transmitted displacement signal for a climb or dive is imparted into an electric automatic pilot until a remotely transmitted signal for termination of operation is introduced to eliminate the displacement signal whereby the craft automatically assumes a level attitude.

The foregoing and other objects and advantages of the invention will appear more-fully hereinafter from a consideration of the detailed description which follows, taken together with the accompanying drawings wherein oneembodiment of the invention is illustrated by way of example. It is to be expressly understood, however, that the drawings are for illustration purposes only, and are not to be construed as defining the limits of the invention, reference being had for this purpose to the appended claims.

In the drawings, wherein like reference numerals refer to like parts:

Figure 1 is a diagrammatic illustration of an electric automatic steering system for mobile craft embodying the novel remotely actuated control unit of the present invention.

Figure 2 is a schematic diagram of the control circuit of the remotely actuated control unit of the present invention.

Referring now to the drawings for a more detailed description of the present invention, the controller unit 9 thereof is illustrated as embodied in an electric automatic pilot providing three axes of control of the character shown and described in aforementioned copending applications.

As more fully described in the aforementioned co-pending applications, the control of rudder H], as shown in Figure l, is derived from a gyro stabilized earth inductor type compass II and a rate of turn gyro pick-oil" l2. Compass II includes an inductive coupling device it having an angularly movable rotor I l, a motor l5 for displacing rotor Id, and a compass signal transmitter [6. The compass signal transmitter 56 is connected to the rudder channel of servo amplifier It, the output of which energizes motor'l9 to operate rudder Ill through clutch 28. The rate of turn signal of pick-oil I2 is also impressed on the rudder channel of servo amplifier 18 in series with the potential of compass signal transmitter l6. Operation of rudder motor I 9 displaces rudder I0 and also an inductive follow-up device 2'! developing in the latter a follow-up potential which is impressed on the rudder channel of amplifier IB in series with the potentials of the compgsszsignal transmitter l6 and rate of turn pick- 0 Signals for operating aileron and elevator surfaces 22 and 23, on the other hand, are developed by bank and pitch take-offs 24 and 25 arranged about the bank and pitch axes of an artificial horizon gyro 26. As a result of a banked condition, take-off 24 develops a bank signal which is communicated to the input of the aileron channel of amplifier 18, the output of the channel being connected to energize a motor 21 which connects through a clutch 28 with aileron surface 22. Operation of motor 21 displaces an inductive follow-up device 29 developing a follow-up signal therein which is impressed on the aileron channel of amplifier la in series with the signal of bank take-01f 24 to modif the operation of motor 21. In a similar manner, as a result of a pitch condition, take-off 25 develops a pitch signal which is communicated to the input of the elevator channel of amplifier 58, the output of the channel being connected to energize a motor 30 which connects through a clutch 3| with elevator surface 23. Operation of motor 30 displaces an inductive follow-up device 32 developing a follow-up signal therein which is impressed on the elevator channel of amplifier IS in series with the signal of pitch take-off 25 to modify the operation of motor 30.

A turn is produced by impressing on the rudder channel of amplifier 18 an independent source of potential having proper magnitude and phase in series with the compass signal transmitter l6, rate of turn pick-off l2 and rudder follow-up device 2|, as will hereinafter be described. When a turn signal is introduced into the automatic pilot, clutch ii is de-energized thereby disconnecting the compass H from the rudder servo system and rudder if! is deflected causing the aircraft to turn at a rate controlled by the rate of turn gyro. The aircraft continues to turn at its impressed rate until the turn signal is terminated whereupon clutch I1 is energized connecting the compass II to the rudder servo system thereby causing the craft to be maintained on the new course.

A bank is brought about by impressing on the aileron channel of amplifier l3 an independent source of potential having the proper magnitude and phase in series with the bank take-off 24 and follow-up device 29. When a bank signal is introduced into the automatic pilot, aileron 22 is deflected causing the aircraft to bank at an angle fixed by the magnitude of the impressed signal. The aircraft remains in the banked condition until the bank signal is terminated whereupon a level attitude is assumed.

A change in pitch is brought about by impressing on the elevator channel of amplifier [8 an independent source of potential having the proper magnitude and phase in series with the pitch take-off 25 and follow-up device 32, to be hereinafter described. When a pitch signal is introduced into the automatic pilot, elevator 23 is deflected causing the aircraft to climb or dive at an angle fixed by the magnitude of the impressed signal. The aircraft will remain in the dive or climb until the pitch signal is terminated whereupon a level attitude is assumed.

The novel control means whereby remotely transmitted displacement signals for any axis of control are introduced into an electric automatic pilot so that the craft control surfaces are deflected in position is designed to operate in conjunction with conventional radio transmitting and receiving equipment. The operators controller may be any type of conventional generating de- 1. Co-ordinated left turn 2. Co-ordinated right turn Skid left turn Skid right turn Climb Dive Termination of operation.

nouns-w The various enumerated operations are characterized by signals of different frequencies. The various amounts of displacement of the craft control surfaces in the operations of co-ordinated left and right turns, climb and dive are each identified by a definite time duration of its characteristic signal. For the skid turns and the termination of operation, it is necessary that their characteristic signals be of continuous time duration terminable by the operator.

The signal modulating, transmitting, receiving and selecting devices per se do not form any part of the present invention and any suitable radiant energy modulating, transmitting, receiving and selecting means may be used.

The displacement signals transmitted from the control station, which may be located either on the ground or in another aircraft, are picked up by the receiver, directed to the proper channel by the selector and inserted into the electric automatic pilot by the novel control unit 9 constituting the subject matter of the present invention. The novel control unit 9 through the movement of potentiometers by small direct current motors operated in response to radio actuated relays impresses an independent source of potential upon the various control channels of amplifier l8 thereby producing displacements of the various control surfaces.

The novel control unit 9 constituting the subject matter of the present invention illustrated schematically in Figure 2, comprises two direct current motors; one-the turn motor 33 driving turn potentiometer 34, aileron potentiometer 35 and elevator potentiometer 35, and the secondthe pitch motor 31 driving pitch potentiometer 38.

Operation of turn motor 33 is controlled by relays 33, 40, 45, 45 and BI, and by limit switches 4|, 42, 43, and 44. Operation of pitch motor 31 is controlled by relays 46, 47, 48, 53 and 6|, and by limit switches 49, 50, 5| and 52. The skid turn signal as distinct from a co-ordinated turn is controlled by relays 39, 43, 54, 55, 56 and 51. Disengagement of clutch I1 and the elimination of compass I i from the control of the automatic pilot during turns is secured when either relay 55 or limit switch 58 is actuated. To vary the speed of pitch motor 3'! and the follow-up ratios of rudder l0, aileron 22 and elevator 23 from those suitable to cruise speed to those suited to wheels down, flaps down condition, relay 59 is employed. In order to vary the rudder off-set to counteract the engine torque at various speeds relays 59 and 6!) are utilized. Since it is necessary to regulate the amount of rudder applied during co-ordinated turns when a speed of 240 knots is attained, relay 60 is used. To provide for quick starting and to maintain proper speed of the pitch motor 31 during cruise conditions, relay I05 is employed. Provision is made for the return of turn motor 33 and pitch motor 3'! to center by the actuation of relay 6| when the automatic pilot is disengaged.

The power to operate the novel control unit 9 is supplied by battery 89 whose positive terminal is connected through switch 90 to load bus BI and negative terminal is grounded. The shunt fields of turn motor 33 and pitch motor 31 are continuously excited from load bus 9 I.

Relay 39 is provided to receive the left turn signal from the selector, while relay 43 receives the right turn signal. Relay 39 is comprised of fixed contact 39A and fixed contact 3913 engaged with movable armature 39C. Relay 40 is comprised of fixed contact 43A and fixed contact 4013 engaged with movable armature 430.

One terminal of the operating coil of relay 33 is connected to the selector where it receives the left turn signal, while the other terminal is connected to ground. Contact 33B is connected to ground, contact 33A is connected to load bus 9|. Armature 39C is connected through armature 53F and contact 55E of relay 55, contact 3 IB and armature 41C of limit switch 4! contact 45E and armature 35]? of relay 5 to terminal 338 of turn motor 33. One terminal of the operating coil of relay 4G is connected to the selector where it receives the right turn signal, while the other terminal is connected to ground. Contact 43B is connected to ground, contact 33A is connected to load bus 3|, while armature 400 is connected through armature 55C and contact 353 of relay 55, contact 423 and armature 42C of limit switch 42, contact 453 and armature 45C of relay '15 to terminal 33A of turn motor 33. When no turn signal is imparted into the novel control unit 9, terminals 33A and 33B of turn motor 33 are grounded. When a left turn signal is imparted into the novel control unit 9, relay 33 is energized causing armature 33C to disengage from contact 393, to break the ground connection, and to engage with contact 33A to supply, for the time duration of the turn signal, potential to operate turn motor 33. At the termination of the turn signal, relay 33 is de-energized causing armature 39C to disengage from contact 39A, to remove the source of potential, and to engage with contact 33B, to ground turn motor 33. The grounding of the terminals of turn motor 33 applies a short-circuit to its armature, to bring turn motor 33 to an immediate stop by dynamic braking.

In like manner when a right turn signal is imparted into the novel control unit 3, relay 553 is energized causing armature 53C to disengage from contact 3313, to break the ground connection, and to engage with contact 33A to supply, for the time duration of the turn signal, potential to operate turn motor 33. At the termination of the turn signal relay is de-energized causing armature 43C to disengage from contact 43A, to remove the source of potential, and to engage with contact MB, to ground the terminals of turn motor 33 to bring it to an immediate stop. The amount of angular displacement of turn motor 33 and consequently the direct connected turn potentiometer 3-3, aileron potentiometer and elevator potentiometer 33 from the center position depends on the time duration of the turn signal.

Adjustable limit switches A! and 42 are provided for either direction of rotation of the turn potentiom'eters. Limit 'switch 4| is comprised of fixed contact 4 IA and fixed contact 4 IB engaged with movable armature MC. Limit switch 42 is comprised of fixed contact MA and fixed contact 42B engaged with movable armature 42C. Contact MA is connected to ground. During a left turn operation of turn motor 33, contact MB is connected through contact 55E and armature 55F of relay 55, armature 39C and contact 39A of relay 39 to load bus 3i. Armature MO is connected through contact AEE and armature 43B of relay 3-5 to terminal 33B of turn motor 33. When the potentiometers 33, 33, and 36 are rotated to their extreme left limit position, insulated arm 92 attached to the shaft of the potentiometers 34, 35 and 33 disengages armature 4 IC from contact MB, to remove the potential from turn motor 33, and causes engagement with contact MA, to ground the armature of turn motor 33 bringing it to an immediate stop.

Contact 12A is connected to ground. During a right turn operation of turn motor 33, contact @213 is connected through contact 353 and armature 55C of relay 35, armature 33C and contact 43A of relay 33 to load bus 9!. Armature 42C is connected through contact 3513 and armature 51; of relay 35 to terminal 33A of turn motor 33. When the potentiometers 34, 35 and 33 are rotated to their extreme right limit position, insulated arm 92 disengages armature 420 from contact 323, to remove the potential from turn motor 33, and causes engagement with contact 32A, to ground the armature of turn motor 33 bringing it to an immediate stop.

It is to be noted that when turn motor 33 is brought to a stop by either limit switch ti or 62, it is free to operate in the opposite direction since the circuit for rotation in the opposite direction is not disturbed. When turn motor 33 is rotated towards center from either of its extreme limit positions, armature M0 or 32C assumes its normal position in respective engagement with contact iB or 32.8.

Relays 58, and limit switches 33, at are previded to return turn motor 33 to center after termination of operation. Relay G6 is comprised of fixed contact 33A and movable armature 33C. Relay 35 is comprised of fixed contacts 35A, 33D, 35G, and fixed contacts 33E, 33E, *iSH respectively engaged with movable armatures 55C, 33F, 35d. Limit switch 33 is comprised of fixed contact 33A and fixed contact 333 engaged with movable armature 33C. Limit switch 43 is comprised of fixed contact 63A and fixed contact MB engaged with movable armature MC. Fixed contacts 33B and 36B are connected to ground, fixed contacts 43A and 33A are connected to load bus 35 and armatures 33C and MC are respectively connected to fixed contacts MD and 35A.

One terminal of the operating coil of relay 4% is connected to the selector where it receives the termination of operation signal, while the other terminal is connected to the ground. The termination of operation signal is continuous unless terminated by the operator by introducing a signal for another turn operation or by cutting off the termination of operation signal. Contact 43A is connected to ground, while movable armature 366 is connected to one terminal of the operating coil of relay 35. The other terminal of the operating coil of relay =35 is connected to load bus 9!. Contact 453 is connected through armature 32C and contact 3213 of limit switch :32, contact 553 and armature 55C of relay 55, armature 33C and contact 30B of relay it to ground. Contact 45E is connected through armature MC and contact MB of limit switch il, contact 55E and armattu'e 55F of relay 55, armature 33C and contact 3913 of relay 39 to ground.

Displacement of the shaft of potentiom'etens 33, 35, 35 off-center fora left turn immediately causes an insulated arm 93 attached to said- 7. aforementioned shaft to disengage armature 440 from contact 443 and to engage contact 44A until the shaft of potentiometers 34, 35, 36 is again returned to center.

When a termination of operation signal is imparted into the novel control unit 9, relay 46 is actuated causing armature 46C to engage with contact 45A to actuate relay 45. The actuation of relay 45 causes armature 45C to disengage from contact 453 and to engage with contact 45A, connected through armature 44C and contact 44A to load bus SI; and causes armature 45F to disengage from contact 45E and to engage with contact 45D, connected through armature 43C and fixed contact 4313 to ground, thus completing a circuit for the reverse rotation of turn motor 33 back to center. Upon the return of the shaft of potentiometers 34, 35, 35 to center, armature 44C disengages contact 44A and engages grounded contact 4413, to short circuit the armature of turn motor 33 bringin it to an immediate stop.

Displacement of the shaft of potentiometers 34, 35, 36 off-center to the right immediately causes an insulated arm 94 attached to said shaft to disengage armature 430 from contact 433 and to engage contact 43A until the shaft of potentiometers 34, 35, 36 is returned to center. The termination of operation signal imparted into the control unit 9 connects terminal 33A through armature 45C, contact 45A, armature 44C, and contact 4413 to ground and terminal 33B through armature 45F, contact 45D, armature 43C and contact 43A to load bus completing the circuit for the reverse rotation of turn motor 33 to center. Upon the return of the shaft of potentiometers 34, 35, 36 to center, armature 43C disengages contact 43A and engages grounded contact 43B, to short-circuit the armature of turn motor 33 bringing it to an immediate stop by dynamic braking.

Relays 39, 45, 54, 55, 56 and 5'! are utilized to produce skid turns. Relay 54 is comprised of fixed contact 54A and movable armature 54C. Relay 55 is comprised of fixed contacts 55A, 55D, 55G, 55M and fixed contacts 55E, 55E, 55H, 55K respectively engaged with movable armatures 55C, 55F, 55J, 55L. Relay 56 is comprised of fixed contact 55A and movable armature 56C. Relay 5'! is comprised of fixed contact 51A and movable armature 510.

One terminal of the operating coil of relay 54 is connected to the circuit selector where it receives the skid signal, while the other terminal is connected to ground. Cont-act 54A is connected to ground, while movable armature 540 is connected to one terminal of the operating coil of relay 55. The other terminal of the operating coil of relay 55 is connected to load bus 9!. Contact 55A is connected through the operating coil of relay 55 to ground. Contact 5513 is connected through contact 42B and armature 42C of limit switch 42, contact 45 and armature 45C of relay 45 to terminal 33A of turn motor 33. Armature 55C is connected through armature 40C and contact 40B of relay 40 to ground. Contact 55D is connected through the operating coil of relay 5'! to ground. Contact 55E is connected through contact MB and armature 4IC of limit switch 4!, contact 45E and armature 45F of relay 45 to terminal 33B of turn motor 33. Armature 55F is connected through armature 39C and contact 39B of relay 39 to ground. Contact 56A and armature 560 are connected across resistor 68, While contact 51A and. armature 51C are con nected across resistor 61 (Fig. 1).

To impart a skid turn signal into the control unit 9, it is necessary to employ two independent continuous signals, first-a skid signal, and second-a turn signal. When a skid" signal is imparted into the control unit, relay 54 is actuated causing armature 54C to engage contact 54A to energize the operating coil of relay 55. The actuation of relay 55 causes armatures 55C and 55F respectively to disengage from contacts 55B and 55E and to engage contacts 55A and 55D, to interrupt the circuit of turn motor 33 and to connect the operating coils of relays 56 and 51 respectively to armature 40C of relay 40 and armature 39C of relay 39.

If a right turn is imparted into the control unit 9, relay 40 is actuated causing armature 40C to disengage contact 40B and to engage contact 40A, connected to load bus 9!, energize relay 56. The actuation of relay 56 causes armature 56C to engage fixed contact 56A to short circuit resistor 68 (Fig. 1) thereby imparting a hard-over right turn signal into the automatic pilot. If a left turn signal is imparted into the control unit, relay 39 is actuated causing armature 39C to disengage contact 39B and to engage contact 35A, connected to load bus 9|, to energize relay 51. The actuation of relay 5'! causes armature 51C to engage fixed contact 51A to short circuit resistor 61 (Fig. 1) thereby imparting a hard-over left turn signal into the automatic pilot. The skid turn signals are maintained continuously until terminated by the operator upon completion of the turn.

When a turn signal is imparted into the automatic pilot by the control unit, it is necessary that the compass H be disconnected from the rudder servo system. To this end limit switch 58 (Fig. 1) is provided to disconnect compass II from the rudder servo system. When a skid turn signal is imparted in the control unit, fixed contact 55H and movable armature 55J of relay 55 are utilized to disconnect the compass I I from the rudder servo system. Limit switch 58 is comprised of fixed contact 583 engaged with movable armature 58C. Contact 55H is connected through clutch I! to ground. Armature 55J is connected through contact 583, movable armature 530, the automatic pilot disconnect switch, to load bus 9|.

In response to a co-ordinated turn signal imparted in the control unit 9, displacement of the shaft of potentiometers 34, 35, 36 off-center in either direction immediately causes an insulated arm turned by the motor 33 to disengage armature 58C from contact 58B to interrupt the circuit energizing clutch l1, thereby disconnecting compass H from the rudder servo system. Armature 580 is maintained in continuous disengagement from contact 58B until the shaft of potentiometers 34, 35, 36 is returned to center by the termination of operation signal.

It is desirable to connect compass H to the rudder servo system immediately when the termination of operation signal is impressed into the control unit 9 thereby eliminating the time lag introduced in returning the shaft of potentiom eters 34, 35, 36 to center. To this end fixed contact 45G and movable armature 45J of relay 45 are utilized and are respectively connected to contact 58B and movable armature 58C. When the termination of operation signal is impressed into the control unit, the actuation of relay 45 by relay 46 causes armature 45J to engage contact 45 thereby energizing clutch l1 in advance of limit switch 58 assuming its normal position. In response to skid signal movable armature 55J is disengaged from fixed contact 55H to interrupt the circuit energizing clutch 11 to disconnect compass I I from the rudder servo system. When the Skid signal is discontinued, relay 55 is deenergized resulting in the immediate engagement of movable armature EiiJ with fixed contact 55H to energize clutch I1.

Relay 41 is provided to receive the climb signal from the circuit selector, while relay 48 receives the dive signal. Relay 51 is comprised of fixed contact 41A and fixed contact 61B engaged with movable armature 41C. Relay to is comprised of fixed contact 63A and fixed contact 383 engaged with movable armature 48C.

One terminal of the operating coil of relay All is connected to the selector where it receives the climb signal, while the other terminal is connected to ground. Contact MA is connected to load bus 91. Contact 413 is connected to ground. Armature NC is connected through contact 498 and armature 49C of limit switch t9, contact 53E and armature 53F of relay 53, to terminal 53B of pitch motor 31. One terminal of the operatin coil of relay 48 is connected to the circuit selector where it receives the dive signal, while the other terminal is connected to ground. Contact 33A is connected to load bus 9!. Contact 48B is connected to ground. Armature 48C is connected through resistor I68, contact 5GB and armature 59C of limit switch 53, contact 53B and armature 53C of relay 53 to terminal 31A of pitch motor 31. When no pitch signal is imparted into the control unit 9, terminals 31A and 31B of pitch motor 31 are grounded.

When a climb signal is imparted into the corn trol unit, relay 41 is energized causing armature 41C to disengage from contact 3113, to break the ground connection, and to engage with contact 41A, to supply, for the time duration of the climb signal, potential to operate pitch motor 31. At the termination of the climb signal, relay l? is tie-energized causing armature 51C to disengage from contact i'iA, to remove the source of potential, and to engage with contact d133, to ground pitch motor 31. The grounding of the terminals of pitch motor 31 applies a short-circuit to its armature, to bring pitch motor 31 to an immediate stop by dynamic braking.

In like manner when a dive signal is imparted into the control unit 9, relay i8 is energized causing armature 43C to disengage from contact 28B, to break the ground connection, and to engage with contact tell to supply, for the time duration of the dive signal, potential to operate pitch motor 31. At the termination of the dive signal, relay 48 is de-energized causing armature i-BC to disengage from contact 48A, to remove the source of potential and to engage with contact i-8B, to ground the terminals of pitch motor 531 to bring it to an immediate stop. The amount of angular displacement of pitch motor 31 and consequently the direct connected pitch potentiometer 33 from the center position is dependent on the time duration of the pitch signal.

Adjustable limit switches at and 5d are provided for either direction of rotation of the pitch po tentiometer 38. Limit switch lil is comprised of fixed contact 49A and fixed contact lElB engaged with movable armature MC. Limit switch 5% is comprised of fixed contact 58A and fixed contact 563 engaged with. movable armature 5418C. Contacts 69A and 50A are connected to ground.

10 During a climb operation of pitch motor 31, contact i913 is connected through armature 51C and contact 61A of relay 41 to load bus 9 l. Armature 35C is connected through contact 53E and armature 5315 of relay 53 to terminal 313 of pitch motor 31. When potentiometer 38 is rotated to its extreme climb limit position, insulated arm attached to the shaft of potentiometer 38 disengages armature 390 from contact 69B, to remove the potential from the pitch motor 31, and causes engagement with contact 59A, to ground the armature of pitch motor 31 bringing it to an immediate stop.

During a dive operation of pitch motor 31, contact 50B is connected through resistor Hill, armature 46C and contact 48A to load bus 9!. Armature 500 is connected through contact 533 and armature 53C of relay 53 to terminal 31A of pitch motor 31. When potentiometer 38 is rotated to its extreme dive limit position, insulated arm 96 disengages armature EEC from contact 5813, to remove the potential from pitch motor 31, and causes engagement with contact bcA, to ground the armature of pitch motor 31 bringing it to an immediate stop by dynamic braking. It is to be noted that when pitch motor 31 is brought to a stop by either limit switch 49 or 58, it is free to operate in the opposite direction since the circuit for rotation in the opposite direction is not disturbed. When pitch motor 31 is rotated towards center from either extreme limit positions, armature 49C or 50C assumes its normal position in respective engagement with contact 493 or 50B.

Relays 4B, 53 and limit switches 51, 52 are provided to return pitch motor 31 to center after termination of operation. Relay 53 is comprised of fixed contacts 53A, 53D and fixed contacts 533, 53E respectively engaged with movable armatures 53C, 53F. Limit switch 51 is comprised of fixed contact 51A and fixed contact 5|B engaged with movable armature 5E0. Limit switch 52 is comprised of fixed contact 52A and fixed contact 52B engaged with movable armature 52C. Contacts EIA and 52A are connected to ground. Armatures 5! C and 520 are respectively connected to contacts 53D and 53A. One terminal of the operating coil of relay 53 is connected to movable armature 46C. The other terminal of the operating coil of relay 53 is connected to load bus 9|.

Displacement of the shaft of potentiometer 38 off-center for a climb causes an insulated arm 91 attached to said aforementioned shaft to immediately disengage armature 520 from contact 52B and to continuously engage contact 52A until the shaft of potentiometer 38 is returned to center.

When a termination of operation signal is imparted into the control unit 9, relay 53 is also actuated by the energization of relay 46. The actuation of relay 53 causes armature 53C to disengage from contact 53B and to engage with contact 53A, connected through armature 52C and contact 52A to load bus 9!, and armature 53F to disengage from contact 53E and to engage with contact 53D, connected through armature MC and contact 5IB to ground, thus completing a circuit for the reverse rotation of pitch motor 31 to center. Upon the return of the shaft of potentiometer 38 to center, armature 52C disengages contact 52A and engages grounded contact 5213 to short-circuit the armature of pitch motor 31 bringing it to an immediate stop.

Displacement'of the shaft of potentiometer 38 of potentiometer 38 is returned to center.

off-center to a dive causes an insulated arm 98 attached to said aforementioned shaft to immediately disengage armature IC from contact 51B and to engage contact 5lA until the shaft The termination of operation signal imparted into the control unit 9 connects terminal 313 through armature 53F, contact 53D, armature 5IC, contact 5|A to load bus 9| and armature 53C, contact 53A, armature 52C and contact 523 to ground, thus completing a circuit for the reverse rotation of pitch motor 31 to center. Upon the return of the shaft of potentiometer 38 to center, armature 51C disengages contact 5IA and engages grounded contact 5IB to short-circuit the armature of pitch motor 3! bringing it to an immediate stop.

Relay 6! is provided to operate turn motor 33 and pitch motor 31 back to center, whenever the automatic pilot is disengaged with either of these motors off-center. Relay 5| is comprised of fixed contact 6|B engaged with movable armature 61C. One terminal of the operating coil of relay 6| is connected through automatic pilot disconnect 99 to load bus 9|, while the other terminal is grounded. Contact 6IB is connected to movable armature 46C of relay 46 to which are also connected one terminal of the operating coils of relays 45 and 53. Armature 6|C is connected to ground.

Whenever either turn motor 33 or pitch motor 31 is ofi-center, a circuit is set up by limit switches 43, 44, 5|, 52, as previously described, for operation back to center. When the automatic pilot is engaged, relay 6! is energized, causing armature BIC to be disengaged from contact 6IB. Disengagement of the automatic pilot with either turn motor 33 or pitch motor 31 is off-center, de-energizes relay 6] causing armature 6! C to engage with contact SIB, to energize relay 45 and 53. The actuation of relays 45 and 53 completes the circuits for the reverse operation of turn motor 33 and pitch motor 31 back to center.

The independent source of potential, required, when the displacement signal is introduced into the automatic pilot, is supplied by transformer 62 (Fig. 1) comprising of primary winding 62A and secondary windings 62B, 62C, 62D, 62E, 62F and 62G. Primary winding 62A is connected to the aircrafts alternating current power supply. Secondary windings 62B, 62C, 62D and 62G are provided with center taps.

Secondary winding 62B impresses a potential through dropping resistors 63, 64, 65 and 66 upon center tapped turn potentiometer 34. One terminal of secondary winding 62B is connected to resistor 65 and through resistor 63 to one terminal of potentiometer 34, while the second terminal of secondary winding 62B is connected to resistor 66 and through resistor 64 to the second terminal of potentiometer 34. The center taps of turn potentiometer 34 and the secondary winding 62B are solidly connected together to increase the safety factor in case of faults and to prevent the center tap of potentiometer 34 shifting from null. The magnitude of the signal voltage tapped ofi between the center tap and movable arm of turn potentiometer 34 is dependent on the values of resistors 63, 64, 65 and 66 and on the displacement of the movable arm of turn potentiometer 34 and its phase dependent on the direction in which the arm is moved. Movement of the arm of turn potentiometer 34 in a direction away from its center tap towards the t r' minal to which resistor 64 is connected produces a potential for a right turn, while movement of the arm in the opposite direction produces a potential for a left turn. The resultant signal potential is impressed upon the rudder channel of amplifier 18 in series with the other rudder signals. Resistors 63 and 64 provide a means of co-ordinating the aircrafts rate of turn set in by the turn potentiometer 34 with the angle of bank set in by the aileron potentiometer 35, the adjustment being independently variable on either side. Resistor 63 may be adjusted to obtain appropriate rudder in a left turn, while resistor 64 for turns towards the right.

To provide for the reduction of the turn signal when the speed of 240 knots is reached, relay 60 (Fig. 2), energized through speed switch lfll actuated by a speed responsive device (not shown), is utilized. Relay 60 is comprised of fixed contacts 60A, 68D, 66G and fixed contacts 68E, 6013, 661-1 respectively engaged with movable armatures 68C, 50F, BilJ. Resistor 65 (Fig. 1) is shortcirouited by contact 663 and armature 600, while resistor 66 is short-circuited by contact 69E and armature 60F.

When a speed of 240 knots is reached, relay 60 is actuated to cause armatures 66C and 66F to respectively disengage from contacts 60B and 60E, removing the short circuits from resistors 65 and 66. The insertion of resistors 65 and 66 into the circuit supplying potential to potentiometer 34, reduces the potential impressed upon potentiometer 34, thereby decreasing the signal potential for any given displacement of the arm of turn potentiometer 34.

Secondary winding 62C impresses a potential through resistors 69 and 10 upon series connected resistors 6! and 68. Across resistor 61 fixed contact 51A and movable armature 51C of relay 5'! are connected, while across resistor 68, fixed contact 56A and movable armature 56C of relay 56 are connected. The center tap of secondary winding 620 is connected through armature 55L and contact 55K of relay 55 to the junction point of resistors 61 and 68. The signal voltage is tapped off between the center tap of secondary winding 62C and the junction of resistors 61 and 68. The short-circuiting of the skid turn signal source by armature 55L and contact 55K of relay 55 when not in use increases the safety factor in case of faults and is broken when the skid signal is introduced into controller 9 energizing relay 55. With armatures 55L, 56C, 510 respectively disengaged from contacts 55K, 56A, 51A, no voltage will appear between the center tap of secondary winding 62C and the junction point of resistors 61 and 68. With armature 56C engaged with contact 56A thus short-circuiting resistor 68 and armatures 55L, 510 respectively disengaged from contacts 55K, 51A, the potential and phase of the resultant signal is such that a hard-over right rudder signal is obtained, while with armature 51C engaged with contact 51A thus short-circuiting resistor 6! and armatures 55L, 560 respectively disengaged from contacts 55K, 56A, the potential and phase of the resultant signal is such that a hardover left rudder signal is obtained. The resultant signal is impressed upon the rudder channel of the amplifier l8 in series with the other rudder signals.

Secondary winding 62D impresses a potential through dropping resistors 1| and 12 upon center-tapped aileron potentiometer 35. The center taps of aileron potentiometer 35 and secondary winding 62D are solidly connected together to increase the safety factor in case of faults and to prevent the center tap of potentiometer 35 shifting from null. The signal voltage is tapped off between the center tap and movable arm of aileron potentiometer 35 and its magnitude and phase is dependent on the values of resistors H and 12 and on the amount and direction of the displacement of the potentiometer arm. Resistors H and 12 provide a means of adjusting the maximum signal from the aileron potentiometer 35, in this way limiting the maximum angle of bank set in by the turn control. Movement of the arm of aileron potentiometer 35 in a direction away from its center tap towards the terminal to which resistor 12 is connected produces a bank signal for a right turn, while movement of the arm in the opposite direction produces a bank signal for a left turn. The resultant signal potential is impressed upon the aileron channel of amplifier H3 in series with the other aileron signals.

Secondary winding 62E impresses a potential upon elevator potentiometer 36. One terminal of secondary winding 62E is connected to the center tap of the elevator potentiometer 35 while the other terminal through dropping resistors 73 and T4. is connected to the opposite end. terminals of elevator potentiometer 38. The signal potential is tapped oif between the center tap and movable arm of elevator potentiometer 36 and its magnitude is dependent on the displacement of the potentiometer arm. The phase of the signal potential is the same to either side of the center tap. As the elevator turn potentiometer 36 is moved, a signal results which calls for an up-elevator correction in each case. The amount of up-elevator correction is independently variable for turns to either side, resistor 13 controlling the amount of up-elevator in a left turn, resistor 14 in a right turn. The resultant signal potential is impressed upon the elevator channel of amplifier IS in series with the other elevator signals.

Secondary winding 62F impresses a potential through resistors 15 and 11 upon resistor 76. Resistors l5 and 16 have each an adjustable tap-off terminal. The rudder offset signal potential is tapped off between the junction of resistors 15 and 16 and the adjustable tap-off terminal of resistor 16 and impressed upon the rudder channel of amplifier [8 in series with the other rudder signals. The rudder offset signal produces a deflection of the rudder for a right turn. At normal cruising conditions with wheels and fiaps raised, to counteract for engine torque a signal corresponding to a rudder offset of approximately 3 is required. To counteract for both engine torque and wheels and flaps down condition, a signal corresponding to a rudder offset of approximately 3 is required.

When a speed of 240 knots is reached, no rudder offset is necessary. To provide for the adjustment of the rudder offset for the different speeds, relay 59 (Fig. 2) and fixed contact 65G and movable armature SUJ of relay B9 are uti1ized. Relay 59 (Fig. 2) is comprised of fixed contacts 59A, 5913, 590+, 59K and fixed contacts 59B, 59E, 59H, 59L respectively engaged with movable armatures 59C, 59F, 59J, 59M. Armature 59C and contact 69G are connected to the junction of resistors 15 and 16, while fixed contact 59A and armature 60J are respectively connected to the adjustable tap-off terminals of resistors 15 and 16.

At cruising speed with wheels and flaps up, relays 59 and 60 are both de-energized, so that armatures 59C and BOJ are respectively dis-engaged from contacts 59A and MG, the rudder offset signal potential tapped off resistor 16 produces a rudder offset of 3. When wheels and flaps are lowered, relay 59, responsive thereto, is energized thereby causing armature 59C to engage contact 59A to short-circuit the tapped section of resistor I5. The short-circuiting part of resistor 15 impresses a greater potential upon resistor 16, thereby increasing the rudder ofiset signal to produce a rudder offset of approximately 8. When a speed of 240 knots is reached, relay 6!! is energized through contacts HJI actuated by speed responsive means (not shown) whereby armature 69.) engages contact 60G to shortcircuit the tapped section of resistor 16 eliminating completely the rudder offset signal.

Secondary winding 52G impresses a potential through dropping resistors 18 and 19 upon centertapped pitch potentiometer 38. The center taps of pitch potentiometer 38 and secondary winding 62G are solidly connected together to increase the safety factor in case of faults and to prevent the center tap of potentiometer 3 5 shifting from null. Resistors l8 and '19 provide a means of adjusting the maximum voltage impressed upon pitch potentiometer 38; resistor 18 controlling dive and resistor 19 controlling climb. The magnitude and phase of signal voltage tapped off between the center tap and movable arm of pitch potentiometer 38 is dependent on the values of resistors 78 and i9 and on the amount and direction of the displacement of the potentiometer arm. Movement of the arm of pitch potentiometer 38 in a direction away from its center tap towards the terminal to which resistor 18 is connected produces a dive signal, while movement of the arm in the opposite direction produces a climb signal. The resultant pitch signal is impressed upon the elevator channel of amplifier E8 in series with other elevator signals.

The ratio of the movement of the control surfaces. to the displacement of the aircraft can be varied both for cruising and for wheels-down, flaps down condition. Switching from one set of ratios to the other is accomplished by means of relay 59. The raising and lowering of the wheels and flaps, operates relay 59, varying not only the rudder, aileron and elevator ratios, but also the amount by which the rudder is oiifset to counteract for engine torque. The ratio for wheels down, flaps down condition is greater than that required for cruising speed. For the same displacement of it is necessary to have a greater movement of the control surfaces for a wheels down, flaps down condition than is required for cruising speed. The ratio of the movement of the control surfaces to the displacement of the aircraft is dependent on the amount of follow-up signal for each control surface. The rudder follow-up potential is impressed by the stator of the rudder follow-up device 2i through resistors 86 and upon resistor 82. Across resistor Bl are connected armature 59C and fixed contact The rudder follow-up signal is taken off resistor 82 and its magnitude dependent upon the actuation of relay For wheels down, flaps down condition, con" tacts H32, actuated thereby, energizes relay 59 causing armature to disengage from contact 598 whereby the magnitude of the rudder followup potential impressed upon resistor 82 is determined resistors 39, iii, 82. For cruising condition, relay 5%} is die-energized so that armature 59C remains engaged with contact 593 to shortcircuit resistor 8i causing the magnitude of the rudder follow-up potential impressed upon resistor 32 to be determined by resistors 80 and 82. Due to the disengagement of armature 59C from contact 5913 when relay 59 is actuated, the rudder follow-up potential impressed upon resistor 82 is less for wheels down, flaps down condition than for cruising condition requiring thereby a larger displacement of the rudder control surface.

The aileron follow-up potential is impressed by the stator of the aileron follow-up device 29 through resistors 83 and 84 upon resistor 85. Across resistor 84 are connected movable armature 59F and fixed contact 59E. The aileron followup signal is taken off resistor 85 and its magnitude dependent upon the actuation of relay 53. For wheels down, fiaps down condition, relay 53 is energized, disengaging armature 59F from contact 5913 to cause the magnitude of the aileron follow-up potential impressed upon resistor 85 to be determined by resistors 33, 8 3, 35. For cruising condition, relay 59 is de-energized so that armature 59F remains engaged with contact 59E to short-circuit resistor 03 causing the magnitude of the aileron follow-up potential impressed upon resistor 85 to be determined by resistors 83 and 85. Due to the disengagement of armature 59F from contact 59E when relay 59 is actuated, the aileron follow-up potential impressed upon re sistor 85 is less for wheels down, flaps down condition than for cruising condition requiring thereby a larger displacement of the aileron control surface.

The pitch follow-up potential is impressed by the stator of the pitch follow-up device 32 through resistors 85 and 81 upon resistor 88. Across resistor 8? are connected movable armature 53J and fixed contact 59H. The pitch follow-up signal is taken off resistor 88 and its magnitude dependent upon the actuation of relay 59.

For wheels down, flaps down condition, relay 59 is energized, disengaging armature 59J from contact 59H to cause the magnitude of the pitch foliow-up potential impressed upon resistor 88 to be determined by resistors 86, 81, 88. For cruising condition, relay 53 is de-energized so that armature 59J remains engaged with contact 59H to short-circuit resistor 87 causing the magnitude of the pitch follow-up potential impressed upon resistor 88 to be determined by resistors 05 and 36. Due to the disengagement of armature 59J from contact 59H when relay 59 is actuated, the pitch follow-up potential impressed upon resistor 38 is less for wheels down, flaps down condition than for cruising condition requiring thereby a larger displacement of the elevator control surface.

For wheels down, flaps down condition, it is desirable that the speed of pitch motor 31 be stepped up. In order to adjust the speed of pitch motor 3?, resistor I (Fig. 2) is inserted in series with its armature. Across resistor I00 are connected movable armature 59M and fixed contact 59K of relay 50. When relay 59 is energized by contacts I02 actuated as a result of wheels down, flaps down condition, armature 59M engages. contact 59K to short-circuit resistor I00 thereby increasing the potential applied across the armature of pitch motor 37. In response to this increase of potential, the speed of pitch motor 31 is stepped When a climb or dive signal is impressed into controller 9 it is desirable to secure a fast response from pitch motor 31. To this end relay I05, comprised of fixed contact IB engaged with movable armature I050, is utilized. Across resistor 16 I00 are connected movable armature I056 and contact I05B. When the pitch signal is applied to either relay 4? or 48, the voltage from load bus 9| is impressed upon the armature of pitch motor 31 through armature I050 and contact I05B producing a quick start.

Due to the time lag of the operating coil of relay I05, armature I056 is disengaged from contact I05B to insert resistor I00 into the armature circuit of pitch motor 3'! to limit its speed after the application of the quick start.

Operation It may be assumed that the craft, upon which the novel controller 9 is employed in conjunction with an all electric automatic pilot, has been flying a level course under the control of an operator located at a station on the ground or in another plane. If the operator desires the craft to make a co-ordinated left turn of A degrees, he inserts such turn into the signal generator which produces a signal having a left turn frequency and a time duration corresponding to A degrees. The signal is modulated, transmitted and picked up by the aircraft receiver. The signal is demodulated by the receiver and passed on to the circuit selector where it is impressed upon the operating coil of relay 39.

Normally the terminals 33B and 33A of the armature of turn motor 33 are connected through movable armatures 33C, 40C and contacts 39B, 30B of relays 33 and 40, respectively to ground so that the armature of turn motor 33 is shortcircuited. When relay 33 is energized, a circuit is set up for the operation of turn motor 33. The ground connection through contact 39B is broken, and terminal 33B of the armature of turn motor 33 is connected through contact 33A to the positive load bus 9| while terminal 33A remains grounded. Turn motor 33 rotates for the time duration of the signal. When the turn signal ends, relay 39 is deenergized whereupon the circuit through contact 33A to load bus 9| is broken and the terminal 333 of the armature of turn motor 33 is again grounded through contact 39B to short-circuit the motor armature bringing it to an immediate stop by dynamic braking.

In consequence of the actuation of turn motor 33, in response to a left turn signal, turn potentiometer 34, aileron potentiometer 35 and elevator potentiometer 35 each connected across independent sources of potential, are displaced from their null positions to produce the displacement signal potentials for the various control surfaces. These displacement signal potentials are impressed upon the rudder, aileron and elevator control channnels of amplifier I8 of the automatic pilot in series with the other signal producing devices to bring about a co-ordinated left turn. The instant that shaft of the potentiometers 34, 35 and 36 is displaced from center, in either direction, insulated arm attached to said shaft, operates limit switch 50 to de-energize clutch I'I thereby removing the compass control from the automatic pilot. The various control surfaces are deflected an amount to correspend with the time of the impressed turn signal. In response to the deflection of the control surfaces, the plane will turn at a rate fixed by such deflection. The amount of deflection of the rudder controls the rate at Which the craft will turn. The craft will continue to turn at the rate fixed by the impressed signal until the turn signal is removed. When the turn signal ends, turn motor 33 and consequently potentiometers 34, 35

and 35 remain displaced from their null positions so that the displacement signals remain im-v pressed upon their respective control channels of amplifier E8 of the automatic pilot until their removal by the operator as will presently appear.

The actuation of turn motor 33 for a left turn sets up a circuit for its operation back to center position by the utilization of limit switches 43 and 44 and relay 45. The instant that the shaft of the potentiometers 34, 35, 35 is displaced for a left turn from center, insulated arm 93, attached to said shaft, disengages armature 440 from grounded contact 4413 to engage contact 44A connected to load bus 9|, while armature 43C remains grounded through contact 4313. The connection of terminals 33A and 33B of the armature of turn motor 33 by means of relay 45 to armatures 44C and 436 respectively completes the circuit for rotation back to center.

When the plane has turned the desired A degrees, the operator sends through a termination of operation signal which is a continuous signal. As aforementioned the termination of operation signal is received and passed on to the circuit selector where it is impressed upon the operating coil of relay 45. Relay 46 energizes relay 45 which connects motor terminals 33A and 33B to armatures 44C and 43C to limit switches 44 and 43, respectively, to produce a rotation back to center.

The instant that turn motor 33 and consequently the shaft of potentiometers 34, 35, 33 is returned to center, insulated arm 93 releases armature 440 from contact 44A, breaking the circuit to load bus 9| and terminal 33A of the armature of turn motor 33 is grounded through contact 4413 to short-circuit the motor armature.

The actuation of relay 45 also energizes clutch I! to introduce the compass into the automatic pilot placing the craft under the control of the compass the instant that termination of operation signal is received. The compass will maintain the craft on its new course. .The return of the turn motor 33 to center removes the displacement signals from their respective control channels of amplifier it of the automatic pilot so that the craft will return to level flight from its banked turn attitude. Upon the return of the shaft of potentiometers 34, 35, 36 to center, insulated arm 95 releases limit switch 58 to maintain the circuit of clutch I! when relay is deenergized upon the end of the termination of operation signal.

If the operator desires the craft to make a coordinated right turn of B degrees, he inserts such turn into the signal generator which produces a signal having a, right turn frequency and a time duration corresponding to B degrees. As aforementioned the signal is received and passed on to the circuit selector where it is impressed upon the operating coil of relay 43. When relay 40 is energized, a circuit is set up for the operation of turn motor 33. The ground connection through contact 403 is broken and terminal 33A of the armature of turn motor 33 is connected through contact 40A to the positive load bus 9|, while terminal 333 remains grounded. Turn motor 33 rotates for the time duration of the signal. When the signal ends, relay 40 is deenergized whereupon the circuit through contact 40A to load bus 91 is broken and terminal 33A of the armature of turn motor 33 is again grounded through contact 403 to short-circuit the motor armature.

The actuation of turn motor 33, in response to a right turn signal, displaces potentiometers 34, 35 and 35 to produce displacement signal potentials for the various control surfaces. These displacement signal potentials are impressed upon the rudder, aileron and elevator control channels of amplifier [8 of the automatic pilot in series with the other signal producing devices to bring about a co-ordinated right turn. The various control surfaces are deflected to correspond with the time of the impressed signal. In response to the deflection of the control surfaces, the plane will turn at a rate fixed by such deflection and will continue to turn at the rate fixed by the impressed signal until the turn signal is removed.

As in the case of a left turn, turn motor 33 and potentiometers 34, 35 and 36 remain displaced from their null positions for a right turn so that the displacement signals remain impressed upon their respective control channels of amplifier 18 until their removal by the operator.

The actuation of turn motor 33 for a right turn sets up a circuit for its operation back to center by the utilization of limit switches 43, 44 and relay 35. The instant that the shaft of the potentiometer 34, 35, 36 is displaced from center for a right turn, insulated arm 94, attached to said shaft, disengages armature 430 from grounded contact 433 to engage contact 43A which is connected to load bus 3|, while armature 44C remains grounded through contact 443. The connection of terminals 33A and 33B of the armature of turn motor 33 by means of relay 45 to armatures 44C nd 430 respectively completes the circuit for rotation back to center.

When the plane has turned the desired B degrees, the operator sends through termination of operation signal. As aforementioned relay 46 energizes relay 45 which connects terminals 33A and 33B of the armature of turn motor 33 to armatures 44C and 43C of limit switches 44 and 43, respectively, to produce a rotation back to center. The instant that turn motor 33 and consequently the shaft of potentiometers 34, 35, 36 is returned to center, insulated arm 94 releases armature 430 from contact 43A breaking the circuit to load bus 9|, and terminal 333 of the rmature of turn motor 33 is grounded through contact 43B to short-circuit the motor armature bringing it to an immediate stop.

Protection against overrunning of potentiometers 34, 35, 33 is provided by limit switches 4i and 42. If during the operation of a left turn, turn motor 33 should run beyond the allowable left limit, insulated arm 92 attached to the shaft of potentiometers 34, 35 and 36 operates limit switch 4! to disconnect terminal 333 from load bus 9i and grounds it through contact 41A to bring it to an immediate stop. In like manner during the operation of a right turn, turn motor 33 is brought to a stop by the operation of limit switch 42.

The skid turn voltage is tapped on between the center tap of secondary winding 62C and the junction of resistors 61 and 68 and impressed upon the rudder channel of the amplifier 13 in series with the other rudder signals. If the operator desires the craft to make a skid turn, it is necessary to insert two signals into the signal generator. The first signal is the skid signal which is a continuous signal. As aforementioned the skid signal is received and passed on to the circuit selector where it is impressed upon the operating coil'of relay 54. Relay 54 energizes relay 55 which disconnects turn motor 33 from the circuit and connects the Operating coils of relays 51 and 56 to the armatures 39C and 40C of relays 39 and 40 respectively. Relay 55 disengages clutch l'l thereby removing the compass from the control of the automatic pilot, and also breaks the connection between the center tap of secondary winding 52C and the junction of resistors 61 and 68.

If it is desired that the craft make a left skid turn, a left turn is then imparted into the signal generator which produces a continuous signal having a left turn frequency. The left turn si nal is received and passed on to the circuit selector where it is impressed upon the operating coil of relay 39. Relay 39 actuates relay shortcircuiting resistor 61 whereby a hard-over left turn signal potential is obtained and impressed upon the rudder channel of amplifier 18 of the automatic pilot to produce a hard-over displacement of the rudder to the left.

When the plane has turned the desired amount, the operator ends the skid turn by terminating the skid signal. Termination of the skid signal de-energizes relay 55 whereby the clutch H is nergized to introduce the compass into the automatic pilot placing the craft under the control of the compass to maintain the new course. The de-energization of relay 55 also reconnects the center tap of winding 620 with the junction of resistors 61 and 68 to eliminate the hard-over left turn signal.

If it is desired that the craft make a right turn, a right turn is imparted after the skid signal into the signal generator which produces a continuous signal having a right turn frequency. The right turn is received and passed on to the circuit selector where it is impressed upon the operating coil of relay 40. Relay actuates relay 56 shortcircuiting resistor 68 whereby a hard-over right turn potential is obtained and impressed upon the rudder channel l8 of the automatic pilot to produce a hard-over displacement of the rudder to the right.

If the operator desires to place the craft into a climb at an angle D, he inserts the climb angle desired into the signal generator which produces a signal having a climb frequency and a time duration corresponding to D degrees. As aforementioned the signal is received and passed onto the circuit selector where it is impressed upon the operating coil of relay 41.

Normally the terminals 31A and 31B of the armature of pitch motor 31 are connected through movable armatures 48C, 41C and contacts 48B, 41B of relays 48 and 41 respectively to ground so that the armature of pitch motor 3! is short-circuited. When relay 41 is energized, a circuit is set up for the operation of pitch motor 31. The ground connection through contact 41B is broken and terminal 31B of the armature of pitch motor 31 is connected through contact 41A to the positive load bus 9|, while terminal 31A remains grounded. Pitch motor 31 rotates for the time duration of the signal. When the climb signal ends, relay 4! is de-energized whereupon the circuit through contact 41A to load bus 9| is broken and the terminal 313 of the armature of pitch motor 31 is again grounded through contact 4113 to short-circuit the motor armature bringing it to an immediate stop.

In consequence of the actuation of pitch motor 31 in response to a climb of D degrees, elevator potentiometer 38, connected across an independent source of potential, is displaced from its null position to create the climb displacement signal potential. This climb displacement signa1 potential is impressed upon the elevator control channel of amplifier l8 of the automatic pilot in series with the other signal producing devices to bring about a climb. The elevator surfaces are deflected to correspond with the impressed climb signal, the plane assuming a climb angle of D degrees, and will remain in that attitude until the climb displacement signal is removed by the termination of operation signal.

When the climb signal ends, pitch motor 31 and consequently elevator potentiometer 38 remains displaced from its null position so that the climb displacement signal remains impressed upon the elevator control channel of amplifier [8 of the automatic pilot until its removal by the operator as will presently be described.

The actuation of pitch motor 31 for a climb, sets up a circuit for its operation back to center position by the utilization of limit switches 5| and 52 and relay 53. The instant that the shaft of the potentiometer 33 is displaced from center for a climb insulated arm 91, attached to said shaft, disengages armature 52C from grounded contact 523 to engage contact 52A which is connected to load bus 9|, while armature 51C remains grounded through contact MB. The connection of terminals 31A and 31B of the armature of pitch motor 31 by means of relay 53 .to armatures 52C and SIC respectively completes the circuit for rotation back to center,

In order to terminate the climb, the operator sends through a termination of operation signal. As aforementioned the termination of operation signal is received and passed on to the circuit selector where it is impressed upon the operating coil of relay 46. Relay 46 energizes relay 33 which connects the terminals 31A and 31B of the armature of pitch motor 31 to armatures 52C and 51C of limit switches 52 and 5| respectively to produce a rotation back to center. The instant that pitch motor 3'! and consequently the shaft of potentiometer 38 is returned to center, insulated arm 91 releases armature 52C from contact 52A, breaking the circuit to load bus SI and terminal 31A is grounded through contact 52B to short circuit the motor armature bringing it to an immediate stop. The return of pitch motor 31 to center removes the climb displacement signal from the elevator channel of amplifier [8 of the automatic pilot whereby the craft automatically assumes a level attitude.

If the operator desires to place the craft into a dive at an angle E, he inserts the dive angle desired into the signal generator which produces a signal having a dive frequency and a time duration corresponding to E degrees. As aforementioned the signal is received and passed onto the circuit selector where it is impressed upon the operating coil of relay 48. When relay 48 is energized, a circuit is set up for the operation of pitch motor 37. The ground connection through contact 48B is broken and terminal 31A is connected through contact 48A to the positive load bus 9|, while terminal 31B remains grounded. Pitch motor 31 rotates for the time duration of the signal. When the signal ends, relay 48 is deenergized whereupon the circuit through 48A to load bus 9| is broken and terminal 31A of the armature of pitch motor 31 is again grounded through contact 48B to short-circuit the motor armature.

In consequence of the actuation of pitch motor 31 in response to a dive of E degrees, elevator potentiometer 38, is displaced from its null position to create the dive displacement signal potential. This dive displacement signal potential is impressed upon the elevator control channel l8 of the automatic pilot in series with the other signal producing devices to bring about a dive. The elevator surfaces are deflected to correspond with the impressed dive signal of E degrees. In response to the deflection of the elevator surfaces, the plane will assume a dive of E degrees and will remain in that attitude until the dive displacement signal is removed by the termination of operation signal.

When the dive signal ends, pitch motor 31 and elevator potentiometer 38 remains displaced from its null position so that the dive displacement signal remains impressed upon the elevator control channel of amplifier [8 of the automatic pilot until its removal by the operator.

The actuation of pitch motor 3'! for a dive sets up a circuit for its operation back to center position by the utilization of limit switches 5| and 52 and relay 53. The instant that the shaft of the potentiometer 38 is displaced from center, insulated arm 98, attached to said shaft, disengages armature 510 from grounded contact 51B to engage contact MA which is connected to load bus 9i, while armature 52C remains grounded through contact 523. The connection of terminals 31A and 31B of the armature of pitch motor 31 by means of relay 53 to armatures 52C and H respectively completes the circuit for rotation back to center.

In order to terminate the dive, the operator sends through a termination of operation signal. Relay 48 will cause energization of relay 53 which connects the terminals 31A and 37B of the armature of pitch motor 31 to armatures 52C and 51C of limit switches 52 and respectively, to produce a rotation back to center. The instant that pitch motor 3'! and consequently the shaft of potentiometer 38 is returned to center, insulated arm 98 releases armature 5|C from contact MA, breaking the circuit to load bus 9! and terminal 313 is grounded through contact 5|B to shortcircuit the motor armature bringing it to an immediate stop. The return of pitch motor 3'! to center removes the dive displacement signal from the elevator channel of amplifier I8 of the automatic pilot whereby the craft automatically assumes a level attitude.

Protection against overrunning of potentiom-- eter 38 is provided by limit switches 49 and 50. If, during the operation of a climb, pitch motor 31 should run beyond the allowable climb limit, insulated arm 96, attached to the shaft of potentiometer 38 operates limit switch 49 to disconnect terminal 3TB of the motor armature from load bus 9! and grounding it through contact 49A bringing it to an immediate stop. In like manher, during the operation of a dive, pitch motor 31 is brought to a stop by the operation of limit switch 58.

Although but one embodiment of the present invention has been illustrated and described in detail, it is to be expressly understood that the invention is not limited thereto. Various changes may be made in the design and arrangement of the parts without departing from the spirit and scope of the invention as will now be understood by those skilled in the art. For a definition of the limits of the invention, reference will be had primarily to the appended claims.

Having thus described our invention, we claim as new and desire to secure by Letters Patent:

1. In an automatic pilot for aircraft having rudder, aileron, and elevator actuating motors controlled by signals developed by direction, turn, and attitude devices, the combination comprising a signal source, reversible motors, a relay circuit connected to said source and said motors for selectively operating said motors, a source of potential, a balanced impedance network in the pilot control circuits of the actuating motors connected to said potential source, said motors being adapted in response to the signal source to unbalance said networks to provide additional signals in the pilot control circuits, make and break means controlled by said relay circuit to disconnect the source of direction signal in the pilot control circuits, and to short a portion of said impedance networks to provide a hard over signal to the rudder actuating motor control circuit.

2. In an automatic pilot for aircraft having rudder, aileron, and elevator actuating motors controlled by signals developed by direction, turn, and attitude devices, the combination comprising a remote signal source, turn relays, a skid turn relay, a climb relay, a dive relay, and a termination relay responsive to the respective signals of said source, a turn reversible motor, and a pitch reversible motor; said motors being controlled by the turn and termination relays, and the climb, dive and termination relays, respectively: balanced impedance networks connected into the direction, turn, and attitude control circuits of the pilot actuating motors including resistors variable by the angular displacement of said motors, the turn motor controlling the variable resistors in the direction and turn circuits; and a source of signal potential for said impedance networks, the variations of the resistors by said motors unbalancing said networks to provide a signal potential altering the pilot signals.

3. In an automatic pilot for aircraft having rudder, aileron, and elevator actuating motors controlled by signals developed by direction, turn, and attitude devices, the combination comprising a signal source, turn relays, a skid turn relay, a climb relay, a dive relay, and a termination relay responsive to the respective signals of said source, a turn reversible motor, and a pitch reversible motor; said motors being controlled by the turn and termination relays, and the climb, dive and termination relays, respectively: balanced impedance networks connected into the direction, turn, and attitude control circuits of the pilot actuating motors including resistors variable by the angular displacement of said motors, the turn motor controlling the variableresistors in the direction and turn circuits; a source of signal potential for said impedance networks, the variations of the resistors by said motors unbalancing said impedance networks to provide a signal potential altering the pilot signals, switch means controlled by said turn motor and make and break means controlled by said skid relay to disconnectv the source of pilot direction signal, and means controlled by said reversible motors and said termination relay for. returning said motors to no signal condition.

4. In an automatic pilot for aircraft having rudder, aileron, and elevator actuating motors controlled by signals developed by direction, turn, and attitude devices, the combination comprising a signal source, turn relays, a skid turn relay, a climb relay, a dive relay, and a termination relay responsive to the respective signals of said source, a turn reversible motor, and a pitch reversible motor; said motors being controlled by the turn and termination relays, and the climb, dive and termination relays, respectively: balanced impedance networks connected into the direction, turn, and attitude control circuits of the pilot actuating motors including resistors variable by the angular displacement of said motors, the turn motor controlling the variable resistors in the direction and turn circuits; a source of signal potential for said impedance networks, the variations of the resistors by said motor unbalancing said networks to provide a signal potential altering the pilot signals, switch means controlled by said turn motor and make and break mean controlled by said skid relay to disconnect the source of direction signal, said last means shorting a portion of the impedance network in the turn circuits to provide a hard-over signal to the rudder actuating motor in response to skid signals, and means controlled by said reversible motors and said termination relay for returning said motors to no signal condition.

5. In an automatic pilot for aircraft having rudder, aileron, and elevator actuating motors controlled by signals developed by direction, turn, and attitude devices, the combination comprising a remote signal source, two turn relays, a skid turn relay, a climb relay, a dive relay, and a termination relay responsive to the respective signals of said source; a turn reversible motor, and a pitch reversible motor; said motors being controlled by the turn and termination relays, and the climb, dive and termination relays, respectively: balanced impedance networks connected into the direction, turn, and attitude control circuits of the pilot actuating motors including resisors variable by the angular displacement of said motors; the turn motor controlling the variable resistors in the direction and turn circuits: a source of potential for said impedance networks, the variations of the resistor by said motors unbalancing said networks to provide a signal potential for altering the pilot signals; switch means controlled by said turn motor and make and break means controlled by said skid relay to disconnect the source of direction signal, said last means shorting a portion of the balanced impedance network in the turn circuits to provide a hard-over signal to the rudder actuating motor in response to skid signals; means responsive to aircraft speed to short another portion of the impedance network to eliminate rudder offset signals when a predetermined airspeed is reached, F

means responsive to a Wheels-down, flaps-down condition for shorting still another portion of the impedance network to increase the rudder offset signals, switches controlled by said reversible motors for limiting the angular displacement thereof, and means controlled by said reversible motors and by said termination relay for returning said motors to no signal condition.

6. In an automatic pilot for aircraft having rudder, aileron and elevator actuating motors controlled by signals developed by direction, turn and attitude devices, the combination comprising a signal source, reversible motors, means connected to said source and to said reversible motors for selectively operating said reversible motors, a source of potential, balanced impedance networks in the pilot control circuits of the actuating motors connected to said potential source, means in said networks actuated by said reversible motors in response to the signal source to unbalance said networks to provide additional signals in the pilot control circuits, and make and break means responsive to the signal source to short a portion of said impedance networks and provide a hard-over signal to the rudder actuating motor.

7. In an automatic pilot for aircraft having rudder, aileron and elevator actuating motors controlled by signals developed by direction, turn and attitude devices, the combination comprising a source of potential, balanced impedance networks in the pilot control circuits of the actuating motors connected to the source of potential, a signal source, means adapted to unbalance said networks in response to the signal source to provide additional signals in the pilot control circuits to control the flight of the aircraft in accordance with the signal source, and make and break means controlled by said signal source to short a portion of said impedance networks and provide a hard-over signal to the rudder actuating motor.

8. In an automatic pilot for aircraft having rudder, aileron and elevator actuating motors controlled by signals developed by direction, turn and. attitude devices, the combination comprising a source of potential, balanced impedance networks in the pilot control circuits of the actuating motors including variable resistors connected to the source of potential, a signal source, reversible motors adapted to vary the resistance of said resistors to unbalance said networks in response to the signal source to provide additional signals in the pilot control circuits to control the flight of the aircraft in accordance with the signal source, and a skid turn relay controlled by said signal source to short a portion of said impedance networks to provide a hard-over signal to the rudder actuating motor.

9. In an automatic pilot for aircraft having rudder, aileron and elevator actuating motors controlled by signals developed by direction and attitude devices, the combination comprising a signal source, reversible motors, a relay network interconnecting said reversible motors and said signal source for selectively operating said reversible motors in response to the signal source, impedances in the actuating motor circuits of the pilot varied by the operation of said reversible motors to vary the operation of the actuating motors in response to the signal source, and means responsive to aircraft speed to short a portion of the impedances to eliminate rudder signals when a predetermined air speed is reached.

10. In an automatic pilot for aircraft having rudder, aileron and elevator actuating motors controlled by signals developed by direction and attitude devices, the combination comprising a signal source, reversible motors, a relay network interconnecting said reversible motors and said signal source for selectively operating said motors in response to the signal source, impedances-in the actuating motor circuits of the pilot varied by the operation of said reversible motors to vary the operation of the actuating motors in response to the signal source, said relay means including a skid relay to short a portion of the impedance in the turn circuits to provide a hard-over signal to the rudder actuating motor in response to skid signals.

11. In an automatic pilot for aircraft having rudder, aileron and elevator actuating motors controlled by signals developed by direction and attitude devices, the combination comprising a signal source, reversible motors, a relay network interconnecting said reversible motors and said signal source for selectively operating said reversible motors in response to the signal source,

impedances in the actuating motor circuits of the pilot varied by the operation of said reversible motors to vary the operation of the actuating motors in response to the signal source, and means responsive to Wheels-down, flaps-down condition for shorting a portion of the impedance in the rudder actuating motor circuit to increase the magnitude of the rudder oiT-set signals.

SABINEW L. BARING-GOULD.

WILLIAM H. SLEEPER, JR.

REFERENCES CITED The following references are of record in the file of this patent:

Number 26 UNITED STATES PATENTS Name Date Mirick Aug. 24, 1926 Loftin June 24, 1930 Hodgman Aug. 29, 1933 Alexanderson May 8, 1934 Fanning Mar. 1, 1938 Busignies Dec. 16, 1941 Dinga Apr. 2, 1946 Roe et a1 May 6, 1947 Moseley July 1, 1947 Moseley July 1, 1947 Young Mar. 15, 1949 

